I think that Reeber hit it and so did JayNelson and all you other guys with ported tracks.
Where did the we come up with idea that your sled is going to have less floatation with a ported track? From less surface area on the snow right?.........a great physics principle but mis-applied to sledding.
These assumptions of less surface area are all predicated on the basis that your sled is sitting stationary on the snow to enjoy those theories of surface area to weight ratio (ported tracks would have less surface area due to the lesser amount of track area on the snow). But none of us ride our sleds stationary, so its a pointless argument, as the track and snow dynamics change as we add speed as a factor in the equation. Once the track has attained any amount of speed, and based on the way a track performs on the snow, many of you would probably change your opinion on ported vs unported.
Most modern rubber paddle tracks bend at the tip slightly, which means the paddles are folding back into the space behind them (when moving forward on the sled, the paddle tips would bend towards the front of the sled). The track is also spinning in the snow towards the rear of the sled, creating voids in the snow behind each paddle. This elevates the track and paddles as it pushes the snow down, away from the flat areas of the track where the ported holes are. More snow is pushed into the space behind each paddle buy the following paddle, but a void space is created. This is what we call an "undeniable truth", and is simply supported due to the fact that sleds dig trenches (holes) and ejecting snow behind them, a void space has to be created in order for more snow to be removed and a deeper hole to be created (this process is repeated rapidly and therefore your sled digs a hole to "China" so to speak).
Depending on track speed and snow conditions, the void created behind each paddle can be larger or smaller depending on many factors. Porting will allow snow to evacuate from the tunnel at the rear idlers much faster than a non-ported track. The momentum at the rear idlers is immense as the track is continually changing direction (180 degrees) which throws the snow against the track. It is also forced out the ported holes by the idlers through mechanical force if the wheels are in the ported spot. Without porting, snow is retained in the track area or exits through the windows only. This is a benefit to the sliders mainly, as more retained snow means more lubrication, although I feel that sufficient lubrication is still (and mainly) provided by the factory windows of the track underneath the rails.
The majority of snow entering the track does not come from the porting within the track, it comes from the sides. Powder snow like BC's will enter the track wherever it can. Harder snow like well setup spring type snow will benefit more from porting IMO as it will not enter through the sides as easily but will be able to be evacuated faster.
There are benefits and drawbacks to both ported and non-ported tracks, however overall the benefits seem to outweigh the drawbacks. Adding any increase in rotating mass and potential for "projectiles" to be coming from your track is not wise IMO. If you think that hooking your ported track on a 1" tree is bad, wait til you spin it on a rock and hook a few of those plugs and tear them loose, scraping the rivets and lexan plugs along your coolers.
Just my engineering thoughts on the subject.
NSC
